Olefin isomerization process

ABSTRACT

A process and catalyst for isomerizing olefinic hydrocarbons while simultaneously hydrogenating polyolefinic hydrocarbons and a method of pretreating and activating the catalyst.

United States Patent [1 1.

Garner et al.

OLEFIN ISOMERIZATION PROCESS Inventors: James W. Garner; Bruce C.

Benedict, both of Bartlesville, Okla.

Assignee: Phillips Petroleum Company, Bartlesville, Okla.

Filed: Sept. 18, 1970 Appl. No.: 73,585

Related US. Application Data Continuation-impart of Ser. No. 743,068, July 8,

1968, abandoned.

U.S. CL. 260/683.2, 260/677 H, 208/143 Int. Cl. C07c 5/30 Field of Search 260/683.2, 677 H;

[ Oct. 9, 1973 [56] References Cited UNITED STATES PATENTS 3,485,887 12/1969 Kronig et a]. A 260/677 3,471,400 10/1969 Cosyns et al.... 208/255 3,076,858 2/1963 Frevel et al 260/677 2,946,829 7/1960 Likins et al. 260/677 Primary Examiner-Delbert E. Gantz Assistant Examiner-Veronica OKeefe Attorney-Young and Quigg [5 7] ABSTRACT A process and catalyst for isomerizing olefinic hydrocarbons while simultaneously hydrogenating polyolefinic hydrocarbons and a method of pretreating and activating the catalyst.

10 Claims, 1 Drawing Figure OLEFIN ISOMERIZATlON PROCESS This is a continuation-in-part of our application Ser. No. 743,068 filed July 8, 1968, now abandoned.

This invention relates to an improved olefin isomerization process. In one of its specific aspects, it relates to an improved catalyst for hydrocarbon isomerization and to a method of pretreating and reactivating the catalyst.

Olefin isomerization, as referred to herein, shall mean the process for shifting the double bond of olefins containing at least four carbon atoms. By the process ment of various olefins or unsaturated hydrocarbons,

including those having a terminal double bond positioned between two nontertiary carbon atoms. Such hydrocarbons are nontertiary in the sense that there is no branching of the carbon atom chain at the doublebonded carbon atoms, although such carbon atom chains may branch at carbon atoms remote from the double bonded carbon atoms.

The radicals attached to such tertiary carbon atoms may be of alkyl, aryl, or aralkyl in character. While the present invention is described in relation to the isomerization of butene-l to butene-2, pentene-l, hexene-l and higher homologs may also be converted according to the process of this invention.

Hydrocarbon stocks may also contain readily polymerizable diolefins and unsaturated hydrocarbons such as butadiene and acetylene, and the like, the presence of which is objectionable when isomerizing. This objection is based upon the tendency of such materials to polymerize during, and to interfere with, the isomerization or to be converted during the isomerization to undesirable forms.

Accordingly, it has been the practice within the art to conduct the process in two steps, the first directed to removal of diolefins or polyolefins, and the second directed to isomerization.

ture levels while introducing hydrogen at a plurality of points.

[none embodiment of this invention, the process is carried out at levels of improved catalyst activity.

Accordingly, it is an object of this invention to provide an improved olefin isomerization processand an improved isomerization catalyst.

It is also an object of this invention to provide an olefin isomerization process in which the activity of the catalyst is beneficially affected by a novel method of treatment.

Additional objects and advantages of this invention will become apparent from its ensuing description.

This invention may be carried out in any of the usual processing sequences, including series or parallel flows of reactants and similar modifications and adaptations generally applicable to hydrocarbon processing. Similarly, provision is made for control of process conditions by the usual instrumentation.

A typical hydrocarbon feed composition suitable for processing according to this invention is one containing saturated hydrocarbons, isobutylene, butadiene, butene-2 in both the'cis and trans forms, butene-l which it is desirable to isomerize the butene-2, and minor amounts of diolefins. Similarly, a typical hydrocarbon feedstock might be one containing propane, propylene, butanes, butenes, 3-methylbutene-l, Z-methylbutene- 1, 2-methylbutene-2, and diolefins such as 1,3- butadiene.

Catalysts suitable for the promotion of the reactions of this process include the noble metals of Group VIII of Periodic Table of Elements, Handbook of Chemistry and Physics, Chemical Rubber Company, 45th Edition 1964), page 8-2 which are ruthenium, rhodium, palla- It is the method of this invention to provide a process of simultaneously carrying out both reactions over a single catalyst, in a single contact step, the isomerization being performed without interference by diolefinic materials or by the products to which such diolefinic material is converted. The advantages of this process over prior art processes include simplification of process equipment, its operation, and minimization of plant investment and operating costs.

By the method of this invention, there is provided a process for isomerizing a monoolefinic hydrocarbon in diurn, osmium, iridium and platinum. Any of the usual catalyst supports can be employed, such including alumina, silica-alumina, glass beads and carbon, although 3 alumina is preferred.

Both pelleted and spherical catalysts have proved satisfactory. A preferred catalyst is palladium on a carrier, preferably alumina. The catalyst will contain about 0.005 to about 1.0 weight per cent palladium on alumina, preferably about 0.01 to about 0.1. The alumina Louisville, Kentucky, and is designated as Catalyst C31 and described in Bulletin No. C3l-O53 and contains about 0.05 weight percent palladium on alumina.

Another satisfactory commercial catalyst is that manufactured by The Girdler Corporation, Louisville, Kentucky, and designated as Catalyst 6-55 and described in Girdler Corporation Data Sheet G-S 5-562 and containing about 0.03 weight per cent palladium on alumina.

The process is conducted at a reaction temperature of about F. to about 450F., preferably about F. to about 380F., and under suitably low pressure conditions while maintaining the hydrocarbon preferably in the vapor phase, although liquid phase operation is satisfactory. Pressures are from about 15 psig to about 250 psig, preferably from about 50 psig to about 160 psig. Hourly space velocities, (VHSV), are maintained from about 100 to about 10,000, preferably from about 1000 to about 2000, based upon standard conditions.

Hydrogen is preferably mixed with the hydrocarbon prior to contacting the catalyst, preferably after vaporization of the hydrocarbon, and can be added undiluted or diluted with an inert gas. Hydrogen is added in amounts of about 0.5 to about 50 mols per hundred mols of hydrocarbon, preferably in amounts of about 3 to about mols per 100 mols of hydrocarbon.

An embodiment of the invention carried out within the ranges set forth is illustrated by the following examples, specifically adapted to the isomerization of butenes and pentenes but illustrative of the general applicability of the process to the feedstocks previously discussed, using the aforementioned Catalyst C31.

The following examples represent some of the best modes for carrying out the invention. 1n each example, the feed stream is a typical olefin-containing charge stream intended for charging to a refinery disproportionation unit.

EXAM PLE 1 A hydrocarbon stream was isomerized in a series of runs under the indicated operating conditions for the purpose of isom eriz ing butenes in the presence of butadiene and butyne-l. Analyses of the feed and product streams are given below:

These data indicate that isomerization, as evidenced by EXAMPLE 1] An embodiment of the invention was carried out within the defined operating conditions and with the defined catalyst but with a feedstock of different composition, it being desired to isomerize butenes in the presence of butadienes, butyne-l and isoprene. Operat- TABLE 1 Run No. 1 2 3 Process Temp, F. I00 160 250 Process Press, psig 110 110 110 Volumetric Hourly Space Velocity 1000 1000 1000 Hydrogen Added, mols/100 mols Hydrocarbon 3.7- 5.3 3.3

Stream Analysis, M01

Product, Run Number Hydrocarbon Feed 1 2 3 Butanes 0.12 0.58 2.32 i 0.34 lsobutylene 41.3 43.6 42.4 42.90 Butcne-l 27.0 11.2 3.41 16.0 trans-Butene-2 11.4 23.2 28.8 20.2 ciS Butene-2 8.9 14.3 14.9 ;13.l Butadiene 3.0 00] 00] 0.01 Butyne-l 0.04 0.01 0.01 0.01 lsoprene 0.03 0.01 0.0l 0.01 Carbon Dioxide 0.15 0.15 0.15 0.15 Pcntanes+ 0.10 0.10 0.10 0.10 Propane 7.96 7.84 7.90 7.18 Total 100.00 100.00 100.00, 100.00 Butene-Z/ Butene-l an increase in the ratio of butene-Z to butene-l, was efvention is a decided advance in the isomerization art in that this process allows the simultaneous performance of the removal of the diolefins or polyole'fins and isom-= erization, in contrast with the two stage process previously required for effecting these objects.

ing conditions and stream analyses were as follows:

TABLE 11 Run No. 1 2 3 Process Temp., "F. 200 200 200 Process Press, psig 110 110 1 10 Volumetric Hourly Space Velocity 1000 1000 1000 Hydrogen Added, mols/ mols Hydrocarbon 4.0 4.7 4.6

Stream Analysis, M01

. Product, Run Number Hydrocarbon Feed 1 2 3 Butanes 0.13 0.29 1.00 0.87 'Butene-l 28.5 24.9 8.7 5.8 tran's-Butene2 1 1.4 15.1 27.4 27.8 cis-Butene-Z 8.8 10.5 15.3 15.2 Butadiene 3.8 0.01 0.01 0.0[ Butyne-l 0.02 0.01 0.01 0.01 lsoprene 0.02 0.0l 0.0l 0.01 Carbon Dioxide 0.15 0.15 0.15 0.15 Other 47.8 49.03 47.42 50.15 Total 100.00 100.00 100.00 100.00 Butene-Z/ Butane-1 0.71 1.03 4.91 7.41 1

EXAMPLE 111 A hydrocarbon stream containing percentages of pentene s in the presence of butenes and isoprene was contacted in the presence of the described catalyst with hydrogen .under the conditions delineated below. Conditions were asfo'llows:

Run No. 1 Process Temp., F. 200 Process Press., psig 1 l0 Volumetric Hourly Space Veloci 1000 Hydrogen Added, mols/100 mols hydrocarbon Stream Analysis, Mol

Hydrocarbon Feed Product, Run No. 1 Propylene & Propane 4.4 4.3 Butanes 0.19 1.07 Butenes 90.51 92.7 1,3-Butadiene 3.61 0.01 3 Methylbutene-1 0.41 0.01 Z-Methylbutene-l 0.41 0.37 2-Methylbutene-2 0.10 1,59 lsoprene 0.36 0.01 Total 100.00 100.00

These data indicate the isomerization of the pentenes by the increase in the 2-methylbutene-2 content with a simultaneous decrease in the diolefinic content of the hydrocarbon stream.

The examples set forth above represent typical results of the process when carried out with single-point hydrogen injection into the hydrocarbon stream. In the preferred embodiment of this invention, the process is carried out while introducing hydrogen into the reaction at a plurality of points within the reaction zone. In a related embodiment, the process is carried out using plural hydrogen introduction into the reaction, the reaction temperature being progressively reduced over the catalyst bed as the reaction proceeds. Both of these aspects decrease hydrogen requirements, the amount of butanes formed by saturation of the diolefins, and increase isomerization.

The rate of isomerization of the process increased with reaction temperature. However, high temperatures shift equilibrium to a higher butene-l content in the product. Accordingly, during the early reaction, when the extent of isomerization to butene-2 is low, high temperatures are advantageous. As the reaction proceedsand the extent of isomerization becomes appreciable with attendantly increased butene-2 to butene-l ratios, high temperatures become disadvantageous. Therefore, it is desirable to operate initially with high temperatures and reaction rates and to decrease temperatures as the course of the reaction proceeds thereby taking advantage of the more favorable equilibrium.

Operation in this manner is advantageously done by employing a reaction gradient of decreasing temperature, even to the extent of employing a plurality of catalyst chambers or individual contact zones. Effective operation in this manner is obtained, however, even if the profile of the reaction zone is only substantially progressive in its decreasing temperature, that is, if there exists within the zone, certain areas in which higher temperatures are employed, although in general, the temperature of the catalytic contact zone tends to decrease from inlet to outlet.

Conjunctive with this embodiment, hydrogen is most effective when introduced into the reaction zone at a plurality of points within the reaction zone. Illustrative of this is the following.

EXAMPLE IV A hydrocarbon feed stream of the general nature of that of Example III was conducted into the reaction zone operated within the foregoing specified conditions, hydrogen being added at a single point prior to the catalyst bed. The butene-2 concentrations of the feed and of the product were measured. The amount of Butene-2 Cone,

mol Effluent Hydrogen Addition Inlet Outlet Butane, mol 7r Single Point 24.8 47.0 0.8+ Multi-Point 24.8 47.5 0.55

These data indicate that multiple hydrogen injection into the reaction zone results in increased isomerization of monoolefmic hydrocarbons at lower hydrogen addition rates and results in lower production rates of saturated hydrocarbons.

To confirm this, another series of runs was conducted as set forth in the following.

EXAMPLE V A hydrocarbon stream of the composition shown below was charged to a single catalyst bed. Hydrogen was added to the hydrocarbon prior to the initial contact with the catalyst. Analyses were made on the effluent product.

The identical hydrocarbon stream was charged to a dual catalyst bed system. A portion of hydrogen was added to the hydrocarbon prior to the initial contact with the catalyst and a portion was added midway between the two catalyst beds. The second bed was maintained at a lower temperature than the first bed.

In each instance, total hydrogen addition and space velocities were equal, catalysts were identical, and overall reaction temperatures comparable, a slightly lower average temperature being employed in the dual catalyst bed system.

Results were as follows:

Feed Analysis, mol

Butanes 0.1 l trans-Butene-Z 13.60 cis-Butene-Z l 1.20 Butene-l 26.30 iso-Butylene 44.5 Butadiene 1 .2 Butynel 0.03 Total C,+ 0.32 Propane i 2.74 Total 100.00 Butene-2/ Butene- 1 0.9

' Operating Conditions Single Bed Dual Bed Inlet Temp., F. 1st. Bed 200 225 2nd. Bed 160 Avg. Temp. 200 193 Pressure, psig l 10 1 l0 Hydrogen Addition, mols/100 mols Hydrocarbon: Before First Bed 1.60 149 Before Second Bed- 0.1 l Added to 2nd. Bed 6.9 Total 1.60 1.60 Space Velocity, Overall, VHSV 1000 1000 Product Analysis, mol

Butanes 0.48 0.48 trans-Butene-2 26.9 31.0 cis-Butene-2 16.1 16.2 Butene-l 9.0 4.8 iso-Butylene 44.4 44.4 Butadiene 0.01 0.01 Butyne-l 0.0l 0.01 Total C 0.3 0.3 Propane 2.8 2.8 Total 100.00 100.00 Butene-Z/ Butene-l 4.8 9.8

These data indicate that under conditions of equal hydrogen addition, even with lower operating temperatures, increased isomerization is obtained with multiple point hydrogen injection. Also, a large proportion of EXAMPLE iv A hydrocarbon feed stream, the analysis of which is set forth in Example V was conducted into the reaction zones, the procedure carried out being identical to that used in Example V except that the quantities of hydro-' gen introduced were larger, and, in the case of the multiple-point injection, a larger proportion of the totalhydrogen was introduced just prior to the second catalyst bed.

Results were as follows:

Operating Conditions These data indicate improved isomerization of the dual bed system over the single bed system in respect t those aspects previously discussed.

On the basis of the above data it has been determined that either a single or a multiple catalyst bed isomerization system is advantageously conducted at catalyst temperatures progressively decreasing from about 450F. to about 120F., the range of about 380F.

V downward to about 160F. being preferred. Operating pressure will be in the range of about psig to about 250 psig, about 50 psig to about 160 psig being preferred, at overall space velocities (VHSH) ranging from about 100 to about 10,000, the preferred range being from about 1,000 to about 2,000.

The number of catalytic contact steps and interrelat- The catalyst concerned herein will possess various degrees of activity depending upon the extent of its prior use. Surprisingly, it has been found that while fresh catalyst possesses a certain selectivity, this selectivity can be increased by pretreatment prior to use. One aspect of this pretreatment involves contacting the catalyst with a gaseous stream containing hydrogen.

The gaseous stream can contain hydrogen in a concentration of about 5 to about 100 per cent, about 50 to about 90 per cent hydrogen being preferred; any inert diluent or mixture of diluents can comprise the balance of the mixture. Temperature of the gas stream is maintained from about 150F. to about 400F., tempe ratures of about 200F. to about 250F. being preferred. Pressures are maintained above about psig, generally from about 75 psig to about 150 psig. Any practical space velocity (VHSV) can be employed, generally about one to about 10 being used for a period of about one minute to about minutes.

In addition to improving the original activity of the catalyst prior to use, such treatment improves isomerization by decreasing hydrogen consumption, decreasedly, the number of points of hydrogen injection, will generally range from two to about six, two to about three generally being optimum as dictated by incremental improvement and cost. Total hydrogen will be introduced at the rate of about 0.5 to about mols per hundred mols of hydrocarbon feed, generally in the range of about 3.0 to about 10 mols per hundred mols of hydrocarbon feed.

Distribution of the hydrogen introduced to the plu rality of injection points will vary with the nature of the feed stock and the configuration of the bed. Generally, however, if two beds are employed, from about 98 to about 75 per cent, generally from about 95 to about 85 per cent of the total hydrogen introduced will be added to the first bed, the remainder being added to the sec- 0nd bed. lf more than two beds are employed, the addition of hydrogen will be in decreasing amounts to suecessive beds. 1 h A f' Hydrogen ll'lJfiCtlOIl into the process can be made at k a plurality of points within a single bed as well as at plurality of points within a multiple bed process ing olefin saturation and, attendantly, decreasing saturated hydrocarbon buildup in the isomerized stream.

EXAMPLE VII it has been found that hydrogen treatment of the catalyst' is beneficial when the catalyst activity has decreased. In this instance, hydrogen treatment restores the catalyst to regain much of its original activity after having been deactivated with a temporary poison such as carbon monoxide or when there has been a break through of diolefins or acetylenes due to insufficient hydrogen in the feed or because the catalyst has become deactivated. in this regard, diolefins and acetylenes appear to act as temporary poisons when they contact the catalyst in the absence of hydrogen.

The effect of this hydrogen treatment is shown below, column 1 indicating the feed composition, column 2 giving the reactor effluent composition prior to hydrogen treatment and column 3 giving the improved reactor effluent composition after the hydrogen treatment.

Hydrocarbon Analysis, Mol Hydrogen Free Basis Product, Product, Before After Charge Hydrogen Hydrogen Component Stock Treat- Treatment merit Butanes 0.12 0.9 0.9 iso-Butylene 45.10 45.0 45.0 Butene-l 25.7 9.0 3.8 t-Butene-2 l4.l 25.7 32.0 c-Butene-Z 10.9 16.4 15.3 Butadiene-l,3 1.0 0.0] 0.0l Butyne-l 0.04 0.0l 0.0 l Vinyl Acetylene 0.05 0.0l 0.01 C,,+ 0.4 0.4 0.4 Other 2.59 2.6 2.6 Total 100.00 100.0 100.0 Butene-Z/ Butene-l 0.97 4.7 l2.5 Butene lsomerization, Basis Orig. Butene 0 64.9 85.2

These data indicate that the hydrogen reactivatedcatalyst gave decidedly improved yields of the isomerization products, that is, of total butenes-2 and produced a product from which a principal portion of the butene- *1 had disappeared, either by isomerization or by suppression of its formation from the diolefins, a principal 1 portion of the diolefinic material having been converted to other forms simultaneously with the isomerization reaction.

The catalyst employed in the process of this invention may be inactivated, or poisoned, in a number of ways, after which its activity may be restored by reactivation or regeneration. Among the compounds which decrease the activity of the catalyst is carbon monoxide. Surprisingly, there is a decided advantage in intentionally contacting the catalyst with carbon monoxide and poisoning it, and thereafter treating the catalyst with hydrogen to regenerate it. Such treatment can be carried out prior to using the catalyst or at any time after initial use. In either instance, treatment of the catalyst by contacting with carbon monoxide and then with hydrogen will impart to the catalyst a selectivity greater than originally possessed by the catalyst.

If the catalyst is treated by contact with carbon monoxide in the vapor phase as differentiated from contact with carbon monoxide contained in a hydrocarbon stream, contact between the catalyst and carbon monoxide can be made in any suitable manner. The carbon gaseous mixture containing about 0.1 to about 10 per cent carbon monoxide with any inert gas as the diluent,

about 1 to about 3 per cent being preferred. Any superatmospheric pressure is satisfactory, as is a temperature about ambient. Contact can be made at space velocities of about 100 to about 10,000 for a period of about 30 minutes to about 300 minutes.

If the carbon monoxide is contained in the hydrocarbon stream, contact between the catalyst and carbon monoxide is made with the carbon monoxide contained from about 0.! per cent to about 10 per cent in the hydrocarbons, the hydrocarbons being of either the saturated or unsaturated type. Contact is made with the carbon monoxide and hydrocarbon in the vapor phase and at pressures about psig to about 200 psig and temperatures corresponding thereto in order to maintain the hydrocarbon in vaporous phase. Contact can be made at space velocities of about 100 to about 10,000 for a period of about mimutes to about 300 minutes. Thereafter, the catalyst is contacted with hydrogen in the manner previously described for effecting catalyst pretreatment.

The treatment of the catalyst as described is applicable to either activation of fresh catalyst which has not been used for isomerization or to the regeneration of catalyst poisoned by carbon monoxide in the stream being isomerized. If the catalyst has been poisoned by the carbon monoxide in the hydrocarbon being treated, further carbon monoxide contact is not required prior to the hydrogen contact, only the hydrogen contact then being necessary.

EXAMPLE Vlll During initial operation with fresh catalyst, activity and selectivity ofthe catalyst improve, reaching a maximum value after a period. This induction period can be significantly shortened by a combined treatment of carbon monoxide and hydrogen, or in other words, an intentional poisoning and regeneration. This is illustrated sured while maintaining a constant n-butane content in the reactor effluent. In each instance, the catalyst was used for isomerizing pure grade butene-l feed.

The isomerization was conducted at 200F., l 10 psig and a space velocity of about 1000 VHSV. The activity of the catalyst is related to the butene-l content of the effluent of specified n-butane concentrations of the effluent. In each instance, regeneration of the catalyst was performed as previously described. Results were as follows:

Butene-l Content of Reactor Effluent, Mol

n-Butane Carbon Monoxide in Reactor Original Poisoned Rcactivated Effluent, Catalyst Catalyst Catalyst Mol In these data, the lower the butene-l content of the reactor effluent, the higher the activity of the catalyst.

Accordingly, these data indicate that the activity of the catalyst was restored after intentionally poisoning with carbon monoxide and regenerating with hydrogen to a level higher than that possessed by the original catalyst, the poisoned and regenerated catalyst possessing an activity about 25 per cent to 30 per cent greater than that possessed by the original catalyst. The process ofa preferred embodiment of this invention will be more easily understood when described with reference to the attached drawing which indicates a schematic flow diagram of the process in its simplest form.

Referring to the FIGURE, catalyst vessels 1 and 2 are dual drum type vessels, vessel 1 containing catalyst beds 3 and 4 and vessel 2 containing catalyst beds 5 and 6. Drum 1 contains partition 7 and drum 2 contains partition 8, each of these partitions dividing the drums into two separate catalyst sections.

It will be assumed for the purpose of this example that drum 1 is being regenerated while drum 2 is bein operated to isomerize hydrocarbons.

The hydrocarbon stream enters through line 9, flow of the hydrocarbon through line 10 to drum 1 being closed off. Flow'is from line 9 through line 11 into drum 2. Hydrogen enters the process through line 13 and into drum 2 by means of line 12 above catalyst bed number 5. Provision is made for hydrogen to enter bed 5 through line 20 and to enter above bed 6 through line 21 and into the midsection of bed 6 through line 22. In a similar manner, though not being so operated, hydrobed 4 through line 24 and at the midsection of bed 4 1 through line 25.

Hydrocarbon entering through line 9 and flowing into drum 2 mixes with hydrogen introduced through line 12 and flows into and down through catalyst bed 5. Flow from'the bottom of catalyst bed 5 after the introduction of hydrogen at the midpoint of bed 5 through line 20 is prevented by partition baffle 8 between beds 5 and 6. Accordinglypthe effluent hydrocarbon and hydrogen from bed 5 flows through line 30 into exchanger 32 and from exchanger 32 back into bed 6 through line 31.

Exchanger 32 is used to adjust the hydrocarbon temperature between beds and 6. If the temperature of the hydrocarbon entering bed 6 is higher than desired, exchanger 32 will operate to cool the hydrocarbon stream. Conversely, if the temperature of the stream from bed Sis lower than desired, exchanger 32 will act to increase the temperature of the stream to bed .6.

Hydrocarbon stream entering bed 6 through line 31 is admixed with additional hydrogen introduced through line 21 and the combined charge flows through bed 6 being mixed with additional hydrogen entering the midpoint of bed 6 through line 22. From the bottom of bed 6, the isomerized material leaves through line 13 and 14 to further processing.

it will be assumed for purposes of 'this example that while drum 2 is operating to isomerize hydrocarbons, drum 1 is being regenerated. It is further assumed for purposes of illustrating the preferred embodiment, that the original catalyst in all four beds was poisoned with carbon monoxide and regenerated with a hydrogen treatment prior to use.

Catalyst in drum 1, having had its activity decreased during isomerization is regenerated in situ. Line 15 is not in use for this regeneration but is normally used to introduce a carbon monoxide containing atmosphere into the drums at such times as fresh catalyst has been placed in vessels 1 and 2.

In the regeneration process presently being carried out, the deactivated catalyst in beds 3 and 4 is contacted with hydrogen introduced through line 17 into line 10. The hydrogen passes down over bed 3, through line 33 into exchanger 35 which is inactive, through line 34 into bed 4 and down across bed 4 and out through line 12 into line from which it is sent to disposal.

When carbon monoxide is introduced into contact with the catalyst for activation purposes, it can be introduced through those conduits by means of which hydrogen is introduced into contact with the catalyst.

These two drums operate alternately, one drum in isomerization operation, one drum is being regenerated or on standby until the catalyst in the other drum requires regeneration. At that point, the hydrocarbon is switched from the drum containing the spent catalyst without meaning to limit the invention thereto. It will be further evident that many modifications and variations can be made to the process as described. These are now, however, considered as being outside of the scope of the invention.

What is claimed is:

1. A process for the catalytic isomerization of monoolefinic hydrocarbons having a terminally-positioned double bond, said hydrocarbons containing at least four carbon atoms and being contained in a feed stream which comprises:

a. contacting a catalyst active for the isomerization of monoolefinic hydrocarbons and comprised essentially of a noble metal of Group VIII with carbon monoxide to substantially deactivate said catalyst;

b. contacting the deactivated catalyst with hydrogen to activate said catalyst for monoolefinic hydrocarbon isomerization; and

c. contacting the activated catalyst with said feed stream comprising monoolefinic hydrocarbons to isomerize said monoolefinic hydrocarbons.

2. The process of claim 1 in which said catalyst comprises palladium on alumina and is contacted with said carbon monoxide in the substantial absence of said feed stream.

3. The process of claim 2 in which said carbon monoxide is contained in a gaseous mixture comprising an inert gas.

4. The process of claim 3 in which said carbon monoxide is contained in said gaseous mixture in an amount within the range of from about 0.1 to about 10 per cent. S. The process of claim 1 in which said catalyst is contacted with said carbon monoxide contained in said feed stream.

6. The process of claim 5 in which said carbon monoxide is contained in said feed stream in an amount within the range of about 0.1 to about 10 per cent.

7. The process of claim 1 in which said catalyst is contacted with said feed stream before said contact with said carbon monoxide.

8. The process of claim 7 in which said contact of said catalyst with said feed stream at least partially deactivates said catalyst.

9. The process of claim 8 in which said feed stream comprises butene-l and said partially deactivated catalyst is contacted with said carbon monoxide.

10. The process of claim 9 in which said catalyst is contacted with hydrogen after said catalyst is contacted with said carbon monoxide to activate said catalyst to an activity from about 25 to about 30 per cent greater than the activity of said catalyst before said contact with said feed stream. 

2. The process of claim 1 in which said catalyst comprises palladium on alumina and is contacted with said carbon monoxide in the substantial absence of said feed stream.
 3. The process of claim 2 in which said carbon monoxide is contained in a gaseous mixture comprising an inert gas.
 4. The process of claim 3 in which said carbon monoxide is contained in said gaseous mixture in an amount within the range of from about 0.1 to about 10 per cent.
 5. The process of claim 1 in which said catalyst is contacted with said carbon monoxide contained in said feed stream.
 6. The process of claim 5 in which said carbon monoxide is contained in said feed stream in an amount within the range of about 0.1 to about 10 per cent.
 7. The process of claim 1 in which said catalyst is contacted with said feed stream before said contact with said carbon monoxide.
 8. The process of claim 7 in which said contact of said catalyst with said feed stream at least partially deactivates said catalyst.
 9. The process of claim 8 in which said feed stream comprises butene-1, and said partially deactivated catalyst is contacted with said carbon monoxide.
 10. The process of claim 9 in which said catalyst is contacted with hydrogen after said catalyst is contacted with said carbon monoxide to activate said catalyst to an activity from about 25 to about 30 per cent greater than the activity of said catalyst before said contact with said feed stream. 